Abstract
Anthropogenic disturbances can have strong impacts on lichen communities, as well as on individual species of lichenized fungi. Traditionally, lichen monitoring studies are based on the presence and abundance of fungal morphospecies. However, the photobionts, as well photobiont mycobiont interactions also contribute to the structure, composition, and resilience of lichen communities. Here we assess the genetic diversity and interaction patterns of algal and fungal partners in lichen communities along an anthropogenic disturbance gradient in Białowieża Forest (Poland). We sampled a total of 224 lichen thalli in a protected, a managed, and a disturbed area of the forest, and sequenced internal transcribed spacer (ITS) ribosomal DNA (rDNA) of both, fungal and algal partners. Sequence clustering using a 97% similarity threshold resulted in 46 fungal and 23 green algal operational taxonomic units (OTUs). Most of the recovered photobiont OTUs (14 out of 23) had no similar hit in the NCBI-BLAST search, suggesting that even in well studied regions, such as central Europe, a lot of photobiont diversity is yet undiscovered. If a mycobiont was present at more than one site, it was typically associated with the same photobiont OTU(s). Generalist species, i.e., taxa that associate with multiple symbiont partners, occurred in all three disturbance regimes, suggesting that such taxa have few limitations in colonizing or persisting in disturbed areas. Trebouxia jamesii associated with 53% of the fungal OTUs, and was generally the most common photobiont OTU in all areas, implying that lichens that associate with this symbiont are not limited by the availability of compatible photobionts in Central European forests, regardless of land use intensity.
Highlights
Lichens are frequently used as bioindicators for air pollution, climatic changes, and other anthropogenic disturbances [1,2]
We detected 46 mycobiont and 23 photobiont operational taxonomic units (OTUs) in 224 lichen samples collected from the three areas in Białowieza Forest (Table 1)
Seven OTUs could be assigned a name based on clustering with the reference internal transcribed spacer (ITS) sequences derived from the algal cultures deposited in SAG or the UTEX culture collection (Table 3), two algal OTUs had previously been reported from other lichens, but are not formally described, and 14 algal OTUs (10 Trebouxia and four Trentepohlia) had no significant hit in GenBank
Summary
Lichens are frequently used as bioindicators for air pollution, climatic changes, and other anthropogenic disturbances [1,2]. The symbiotic association consisting of a fungal partner (mycobiont) and a photosynthetic partner (photobiont) is sensitive to changes in substrate properties and microclimatic conditions. Morphological identification of specimens could bias diversity estimates, because cryptic (= molecular) diversity is not regarded. This approach neglects an assessment of the associated microalgae, which may contribute to geographic distribution, and community composition of lichenized fungi [11,12]. A more comprehensive understanding of lichen communities requires an assessment of the diversities, distributions, and interactions of both partners since the availability of compatible algae is a prerequisite for the establishment and maintenance of lichen populations
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